# init(8)

## NAME

         init - grandparent of all processes

## DESCRIPTION

         The first program started by Minix is init.   The  actions  performed  by
         init can be summarized by this pseudo shell program:

              # Open 0, 1, 2.
              exec </dev/null >/dev/log 2>&1

              # Run the system initialization script.
              sh /etc/rc $bootopts

              >/etc/utmp
              echo reboot >>/usr/adm/wtmp

              while :; do
                      # Wait for a process to exit, but don't always block.
                      wait

                      # Record logout.  (Not in this dumb way, of course.)
                      if "pid is in my tables" $pid
                      then
                              echo "logout $pid" >/etc/utmp
                              echo "logout $pid" >>/usr/adm/wtmp
                      fi

                      # Start a new session.
                      while read line type getty init
                      do
                              if idle $line
                              then
                                      $init ... <$tty >$tty
                                      $getty <$tty >$tty 2>&1 &
                                      pid=$!
                                      "add pid to tables" $pid
                                      echo "login $line $pid" >/etc/utmp
                                      echo "login $line $pid" >>/usr/adm/wtmp
                              fi
                      done < /dev/ttytab
              done

         The first action of init is to run /etc/rc to initialize  the  system  as
         described  in boot(8).  Init then enters its main loop where it waits for
         processes to exit, and starts processes on each  enabled  terminal  line.
         The  file /etc/ttytab contains a list of terminal devices, their terminal
         types, the program to execute on them to  allow  one  to  login  (usually
         getty(8)),  and  the  program  to  execute  first  to initialize the line
         (usually stty(1)).  These fields may be left out to indicate that a  line
         is  disabled  or  that initialization is not necessary.  The commands are
         searched using the path /sbin:/bin:/usr/sbin:/usr/bin.

         Init accepts several signals that must be sent to process id 1.   (It  is
         the first process, so natually its process id is 1.)  The signals are:

         SIGHUP
              When receiving a hangup signal, init will forget  about  errors  and
              rescan  ttytab  for  processes  to  execute.   Init normally rescans
              ttytab each time it feels the need to  respawn  a  process,  so  the
              hangup  signal is only needed if a line has been shut down, or after
              a terminate signal.  Note that after turning a  line  off  you  will
              have to kill the process running on that line manually, init doesn't
              do that for you.

         SIGTERM
              Normally sent by programs that halt or reboot Minix.  Causes init to
              stop spawning new processes.

         SIGABRT
              Sent by the keyboard driver when the CTRL-ALT-DEL key combination is
              typed.   Causes  init  to  run the shutdown command.  A second abort
              signal makes init halt the system directly with a system call.   The
              keyboard  driver  halts  the system, without a sync, after the third
              CTRL-ALT-DEL.

      Minix vs. Minix-vmd
         There are a few differences between standard Minix and Minix-vmd  on  how
         init  is  run.   The  /etc/rc  file is executed under standard Minix with
         input connected to  /dev/console,  but  under  Minix-vmd  this  is  still
         /dev/null.  This means that under Minix-vmd processes must be reconnected
         to /dev/console with the intr program  if  they  need  user  interaction.
         Minix-vmd  passes  the  value  of  the bootopts boot variable to /etc/rc.
         Standard Minix does not.

## FILES

         /etc/ttytab              List of terminals devices.

         /etc/utmp                List of currently logged in users.

         /usr/adm/wtmp            Login/logout history.

## SEE ALSO

         ttytab(5), utmp(5), getty(8), stty(1), boot(8).

## AUTHOR

         Kees J. Bot (kjb@cs.vu.nl)